1. Field of the Invention
The present invention relates to a magnetooptical recording medium which performs readouts by utilizing a magnetic Kerr effect, magnetic Faraday effect, and magnetooptical effect. Particularly it relates to a magnetooptical recording medium comprising an antireflection film for improving recording and readout efficiencies.
2. Description of the Prior Art
Amorphous alloy films have hitherto been regarded as being promising from the viewpoint of recording efficiency and readout efficiency. Particularly, a ternary amorhpous alloy film constituted of Gd-Tb-Fe ternary system is a good recording medium because of the low Curie point of about 150.degree. C. and a large Kerr rotation angle. However, it has deficiencies in improving recording sensitity in a single use of a magnetic recording layer and of improving S/N ratio on reading out. An increase in efficiency has been attempted by selecting a combination of a substrate material, a heat insulation layer, an antireflection film, a reflection-increasing film (for utilizing Faraday effect), and so on.
A monolayer antireflection film disposed on a magnetic film was proposed in Japanese Laid-open Patent Publication No. 156943/1981 etc. However, it has a defect of low refraction coefficient and the concomitant low efficiency caused by the difficulty of heating in film forming processes when glass or plastic is used as an outer medium at the recording side.
The inventors of the present invention previously found a Gd-Tb-Fe-Co quaternary amorphous alloy thin film to be a magnetooptical recording medium having a large Kerr rotation angle and sufficient squareness. This quaternary medium has still has deficiencies in a of high Curie point of approximately 300.degree. C. and low recording efficiency.